Panel drive circuit

Abstract

[Problem] To enable unevenness correction to be appropriately performed at a stage after gamma correction even if the output voltage range of a D / A conversion means is variable. [Solution] A panel driving circuit 4 comprises: an input interface 6 to which an image signal is inputted; a gamma correction circuit 8 which corrects an image-processed signal obtained by image-processing the input signal inputted to the input interface 6 by an image processing circuit 7 such that the image-processed signal has a predetermined gamma characteristic; an unevenness correction circuit 9 which corrects a gamma-corrected signal corrected by the gamma correction circuit 8 on the basis of correction data for reducing unevenness of a display panel 2; and a D / A converter 10 which D / A converts an unevenness-corrected signal corrected by the unevenness correction circuit 9 and outputs the D / A converted unevenness-corrected signal to the display panel 2, and has a variable output voltage range. The unevenness correction circuit 9 changes a correction method according to the output voltage range of the D / A converter 10.

Description

Technical Field

[0001] The present invention relates to a panel driving circuit incorporated in a display panel for performing unevenness correction based on correction data.

Background Art

[0002] Panel driving circuits (semiconductor integrated circuits) of display panels such as liquid crystal panels and organic EL panels generally include a gamma correction circuit for setting gamma characteristics (gamma values) according to the characteristics of each individual display panel. Further, in a panel driving circuit, there is one including an unevenness correction circuit for correcting luminance unevenness and color unevenness occurring at the hardware level by superimposing data of the reverse phase of unevenness on the original image for each region or pixel of the display panel.

[0003] In a panel driving circuit including a gamma correction circuit and an unevenness correction circuit, when the unevenness correction circuit is in front of the gamma correction circuit (performs processing first for an external input), the luminance characteristics of the display panel with respect to the output of the unevenness correction circuit are known as the product specifications of a panel module combining the panel driving circuit (particularly the gamma correction circuit) and the display panel (generally, before performing unevenness correction, parameters are determined so that the gamma correction circuit is adjusted to have predetermined gamma characteristics, and individual differences of the product are suppressed). Therefore, unevenness correction in the unevenness correction circuit can be performed using this. For example, if the luminance characteristics of the panel with respect to the input are the curve characteristics of γ (gamma value) = 2.2 as the product specifications of the panel module, a differential value (dL / dV) indicating the change in luminance (dL) with respect to the change in the input digital value (dV) is determined. Thus, the unevenness correction circuit may calculate correction data based on the differential value and perform unevenness correction.

[0004] However, if you want to obtain a display with gamma characteristics other than the once-set gamma characteristics (gamma value), for example, if you want to change the gamma characteristics to obtain a display that is easier to view outdoors in bright light, you must change the settings of the gamma correction circuit. At this time, however, it is necessary to perform the unevenness correction after generating correction data adjusted to the gamma characteristics after the change, and there is a problem that the algorithm of the unevenness correction becomes complicated.

[0005] On the other hand, as a panel drive circuit in which the unevenness correction circuit is located downstream of the gamma correction circuit, there is a panel drive circuit described in Patent Document 1. In this panel drive circuit, when performing unevenness correction at a stage subsequent to gamma correction, it is possible to perform unevenness correction according to the characteristics of each display panel while suppressing an increase in cost and an increase in manufacturing time.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, in recent years, in order to improve the accuracy of luminance control of a display panel, a system has emerged in which the output voltage range of D / A conversion means (D / A converter) is variable. When the panel drive circuit described in Patent Document 1 is directly applied to such a system, there is a problem that when the output voltage range is changed, the unevenness correction by the unevenness correction circuit is not properly performed, and the unevenness may not decrease or may increase.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a panel drive circuit capable of appropriately performing unevenness correction at a stage subsequent to gamma correction even when the output voltage range of the D / A conversion means is variable.

Means for Solving the Problems

[0009] To solve the above problems, the panel driving circuit according to the present invention includes an image signal input unit to which an image signal is input, and for the image signal input to the image signal input unit or a first processing signal obtained by performing a first process on the image signal input to the image signal input unit, gamma correction means for correcting it to have a predetermined gamma characteristic, and for the gamma correction signal corrected by the gamma correction means or a second processing signal obtained by performing a second process on the gamma correction signal corrected by the gamma correction means, unevenness correction means for correcting it based on correction data for reducing unevenness of the display panel, and D / A conversion means for D / A converting the unevenness correction signal corrected by the unevenness correction means and outputting it to the display panel, and the D / A conversion means having a variable output voltage range, wherein the unevenness correction means is characterized by changing a correction method according to the output voltage range of the D / A conversion means.

[0010] The unevenness correction means has an unevenness correction table corresponding to the case where the output voltage range is a reference voltage range V0. When the output voltage range is V0, the gamma correction signal or the second processing signal and a difference signal obtained by correcting the gamma correction signal or the second processing signal with reference to the unevenness correction table are added to generate the unevenness correction signal. When the output voltage range is V different from V0, the gamma correction signal or the second processing signal and a signal obtained by multiplying the gamma correction signal or the second processing signal by an input coefficient V / V0 are corrected with reference to the unevenness correction table, and then a difference signal multiplied by an output coefficient V0 / V is added to generate the unevenness correction signal.

Effect of the Invention

[0011] According to the panel driving circuit of the present invention, even when the output voltage range of the D / A conversion means is variable, unevenness correction can be appropriately performed at a stage subsequent to gamma correction.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

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Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0013] Embodiments for carrying out the present invention will be described with reference to the drawings.

[0014] FIG. 1 shows an unevenness correction system according to the present embodiment. This unevenness correction system 1 corrects an image signal input to a display panel 2 composed of a liquid crystal panel based on correction data, and generates the correction data in order to reduce the unevenness of the display panel 2. It has a panel drive circuit 4 incorporated in the display panel 2 to constitute a panel module 3 and an unevenness correction device 5.

[0015] As shown in FIG. 2, the panel driving circuit 4 includes an input interface 6 to which a digital image signal is input, an image processing circuit 7 that processes the image signal input to the input interface 6, and a gamma correction circuit 8 that refers to a gamma table 8a set according to the characteristics of the individual display panel 2 in which the panel driving circuit 4 is incorporated, and performs gamma correction on the image processing signal processed by the image processing circuit 7 so as to have a predetermined gamma characteristic. A non-uniformity correction circuit 9 refers to a correction table 9a in which correction data for reducing non-uniformity of the display panel 2 is recorded, and performs non-uniformity correction on the gamma correction signal gamma-corrected by the gamma correction circuit 8. A D / A converter 10 that D / A-converts the non-uniformity correction signal non-uniformity-corrected by the non-uniformity correction circuit 9 and outputs it to the display panel 2 and has a variable output voltage range is provided.

[0016] The non-uniformity correction circuit 9 changes the correction method according to the output voltage range of the D / A converter 10. Here, as the correction table 9a, the non-uniformity correction circuit 9 has a corresponding one for the case where the output voltage range of the D / A converter 10 is the reference voltage range V0. When the output voltage range is V0, a non-uniformity correction signal is generated by adding the gamma correction signal and a difference signal obtained by correcting the gamma correction signal with reference to the correction table 9a. When the output voltage range is changed to V different from V0, the gamma correction signal and the product of the gamma correction signal and the input coefficient V / V0 are corrected with reference to the correction table 9a, and then a difference signal multiplied by the output coefficient V0 / V is added to generate a non-uniformity correction signal.

[0017] The non-uniformity correction device 5 is provided with a pattern generator 11 that outputs a digital image signal to the input interface 6 while being connected to the panel driving circuit 4, a control unit 13 that integrally controls the pattern generator 11 and an individual image pickup device camera 12 (see FIG. 1) that picks up an image of the display panel 2, and generates correction data, and a correction data writing unit 14 that writes the correction data generated under the control of the control unit 13 into the correction table 9a of the non-uniformity correction circuit 9.

[0018] When generating correction data, as shown in FIG. 3, the control unit 13 of the unevenness correction device 5 outputs an 8-bit digital image signal of the unevenness correction image (e.g., raster image) to the input interface 6 by the pattern generator 11 (step 1 (described as "S.1" in FIG. 3; the same applies hereinafter)).

[0019] The image signal input to the input interface 6 is subjected to image processing by the image processing circuit 7 (steps 2 and 3) and input to the gamma correction circuit 8 as an image processing signal. In the gamma correction circuit 8, gamma correction is performed on the input image processing signal with reference to the gamma table (step 4) and output to the unevenness correction circuit 9. In the unevenness correction circuit 9, unevenness correction is performed on the input gamma correction signal with reference to the correction table 9a, and the generated 12-bit unevenness correction signal is output to the D / A converter 10 (FIG. 4). At this time, since no correction data is input to the correction table, unevenness correction is not actually performed, and the unevenness correction signal coincides with the gamma correction signal (step 5).

[0020] In the D / A converter 10, D / A conversion is performed on the input unevenness correction signal with the output voltage range being V0 (step 6), and the generated analog image signal is output to the display panel 2, and the unevenness correction image is displayed on the display panel 2 (step 7).

[0021] Subsequently, the control unit 13 captures the unevenness correction image displayed on the display panel 2 with the camera 12 (step 8), determines the luminance of each pixel of the display panel 2 based on the captured image of the camera 12 by, for example, the method described in Japanese Patent Application Laid-Open No. 2016-004037 (step 9), and generates correction data based on this luminance (step 10). It is desirable to obtain the correction data for each predetermined gradation by displaying and capturing the unevenness correction image a plurality of times while changing the gradation.

[0022] Then, the control unit 13 writes the generated correction data into the correction table 9a of the unevenness correction circuit 9 by the correction data writing unit 14 (step 11), whereby the panel driving circuit 4 can perform unevenness correction on the input image signal based on the correction data.

[0023] During unevenness correction, when the output voltage range of the D / A converter 10 is the reference voltage range V0, the unevenness correction circuit 9 adds an input signal (gamma correction signal) and a difference signal obtained by correcting the input signal with reference to the unevenness correction table 9a to generate an output signal (unevenness correction signal). However, when the output voltage range of the D / A converter 10 is changed to V different from V0, the input signal and the product of the input signal multiplied by the input coefficient V / V0 are corrected with reference to the correction table 9a, and then the difference signal multiplied by the output coefficient V0 / V is added to generate an output signal.

[0024] For example, as shown in FIG. 5, assume that the luminance when the output voltage range is V is equivalent to 50% of the luminance when the output voltage range is V0 (V:V0 = 50:100). Also, in the unevenness correction circuit 9, when the output voltage range is V0, when the level of the input signal is 100 (let the luminance be L), the level of the difference signal obtained by referring to the correction table 9a is 10 (the level of the output signal is 100 + 10 = 110), and when the level of the input signal is 50 (the luminance becomes 0.5L), the level of the difference signal obtained by referring to the correction table 9a is 4 (the level of the output signal is 50 + 4 = 54). At this time, when the output voltage range is changed to V, even if the level of the input signal is 100, since the luminance is 0.5L, it is necessary to obtain the corresponding difference signal (level 4) from the correction table 9a. Since the difference signal for the luminance 0.5L can be obtained by referring to the correction table 9a assuming that the level of the input signal is 100×0.5 = 50, as shown in FIG. 6, the unevenness correction table 9a is referred to at the level 50 obtained by multiplying the level 100 of the input signal by the input coefficient V / V0 = 0.5 / 1 = 0.5 to obtain the difference signal of level 4. The difference signal obtained in this way is prepared so that a correct luminance correction result can be obtained when the output voltage range is V0. Therefore, when the output voltage range is V, the luminance correction amount becomes V / V0 = 0.5 / 1 = 0.5 times. Thus, it is multiplied by the output coefficient V0 / V = 1 / 0.5 = 2 to correct it to the difference signal of level 8, and this is added to the input signal to generate the output signal of level 108.

[0025] The panel driving circuit 4 according to this embodiment includes an input interface 6 to which an image signal is input, and a gamma correction circuit 8 that corrects an image processing signal obtained by the image processing circuit 7 processing the image signal input to the input interface 6 so as to have a predetermined gamma characteristic. For the gamma correction signal corrected by the gamma correction circuit 8, a non-uniformity correction circuit 9 corrects it based on correction data for reducing non-uniformity of the display panel 2. A D / A converter 10 that D / A-converts the non-uniformity correction signal corrected by the non-uniformity correction circuit 9 and outputs it to the display panel 2, and the D / A converter 10 has a variable output voltage range. The non-uniformity correction circuit 9 changes the correction method according to the output voltage range of the D / A converter 10. Therefore, even though the output voltage range of the D / A converter 10 is variable, non-uniformity correction can be appropriately performed according to the changed output voltage range at a stage subsequent to gamma correction.

[0026] In this embodiment, specifically, the non-uniformity correction circuit 9 has a correction table 9a corresponding to the case where the output voltage range is the reference voltage range V0. When the output voltage range of the D / A converter 10 is V0, the non-uniformity correction signal is generated by adding the gamma correction signal and a difference signal obtained by correcting the gamma correction signal with reference to the correction table 9a. On the other hand, when the output voltage range is V different from V0, the gamma correction signal and a signal obtained by multiplying the gamma correction signal by the input coefficient V / V0 are corrected with reference to the correction table 9a, and then a difference signal multiplied by the output coefficient V0 / V is added to generate the non-uniformity correction signal. Thus, even when the output voltage range is changed to V, appropriate non-uniformity correction corresponding thereto is performed.

[0027] As described above, the embodiments for carrying out the present invention have been illustrated. However, the embodiments of the present invention are not limited to those described above, and may be appropriately changed without departing from the spirit of the invention.

[0028] For example, in the above embodiment, the display panel 2 is a liquid crystal panel, but the display panel 2 may be an organic EL panel, a plasma display panel, a mini LED panel, a micro LED panel, etc. In the gamma correction circuit 8, in order to ensure the accuracy after conversion by gamma correction, an 8-bit input signal is output as 12 bits, but it may be any information amount such as 10 bits, 11 bits, 14 bits instead of 12 bits.

[0029] Also, the image processing by the image processing circuit 7 may be any processing, and the processing may be performed after the gamma correction circuit 8 (before the unevenness correction circuit 9) instead of before the gamma correction circuit 8, or may be performed before and after the gamma correction circuit 8. The gamma table 8a is not limited to a single table and may be a multi-table in which a plurality of reference destinations are switched.

Explanation of Signs

[0030] 2 Display panel 4 Panel drive circuit 6 Input interface (image signal input section) 8 Gamma correction circuit (gamma correction means) 9 Unevenness correction circuit (unevenness correction means) 9a Correction table (unevenness correction table) 10 D / A converter (D / A conversion means)

Claims

【Claim 1】 An image signal input unit to which an image signal is input; Gamma correction means for correcting an image signal input to the image signal input unit or a first processed signal obtained by performing a first process on the image signal input to the image signal input unit so as to have a predetermined gamma characteristic; Mura correction means for correcting a gamma correction signal corrected by the gamma correction means or a second processed signal obtained by performing a second process on the gamma correction signal corrected by the gamma correction means based on correction data for reducing mura of a display panel; D / A conversion means for D / A converting the mura correction signal corrected by the mura correction means and outputting the converted signal to a display panel, the D / A conversion means having a variable output voltage range; The unevenness correction means has a non-uniformity correction table in which correction data in the case where the output voltage range is the reference voltage range V ０ is written. When the output voltage range is V ０ in this case, the gamma correction signal or the second processing signal and a difference signal obtained by referring to the mura correction table for the gamma correction signal or the second processing signal are added to generate the mura correction signal, When the output voltage range is different from V ０ a difference signal obtained by referring to the unevenness correction table for the gamma correction signal or the second processing signal and the gamma correction signal or the second processing signal multiplied by an input coefficient V / V ０ is added to a signal obtained by multiplying the signal obtained by referring to the unevenness correction table by an output coefficient V ０ / V to generate the unevenness correction signal. A panel driving circuit characterized by this.

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